Laboratories routinely stain biological tissue specimens deposited on laboratory slides for subsequent pathologic examination to detect and/or monitor tissue abnormalities. An immuno histo chemistry (IHC) tissue processing apparatus is used to process samples for immuno-histological reaction staining. An IHC tissue processing system may also be referred to in the art as a slide stainer. Automated tissue processing systems allow batch processing of large numbers of slides containing tissue specimens for subsequent examination. In the course of a process, the tissue specimens are exposed to a series of well-defined processing steps that ultimately produces a properly processed specimen for examination. Automation of the process significantly reduces the time required to process tissue specimens, reduces the incidence of human error and allows processing parameters to be altered in an efficient manner. Improvements to tissue processing systems are continually sought in the interest of reliability, performance, speed and cost.